This application in general relates to a rotary adsorption unit for removing impurities from a gas flow, wherein the desorb function is performed by a closed loop air flow.
Rotary adsorption units, or rotary concentrators, are utilized to remove impurities from an air flow. It is typical that the rotary adsorption unit will include a number of blocks formed of a material that removes impurities from the air flow. The air to be cleaned is passed over the adsorption blocks. The adsorption unit continually rotates and the air to be cleaned is passed onto the adsorption unit over the majority of its rotary path of travel. A desorb or cleaning air flow is passed over the adsorption unit over a relatively small portion of the rotary path of travel of the unit. The desorb air is typically at a much higher temperature than the air to be cleaned, and removes the impurities from the block material.
The desorb air concentrates the impurities removed from the greater volumes of air flow that are cleaned by the adsorption unit. Flow ratios of air to be cleaned to desorb air are typically on the order of 5:1 to 15:1.
The prior art desorb air has been sent to a treatment unit, which removes the impurities from the desorb air. In one standard treatment unit, the desorb air is heated to burn the impurities. That heated clean air is then directed to a heat exchanger, which heats the desorb air then passing to the rotary adsorption unit. With such systems, complicated connections and control are necessary. Moreover, with the prior art systems the cleaned air, after completing its desorb function, is typically passed back to atmosphere. It is desirable to minimize the amount of air exposed to any such process that is passed back to the atmosphere, as there is always the possibility of escape of impurities or pollutants to the atmosphere. Moreover, the prior art systems which utilize heat transfer between the previous desorb air and the desorb air leading to the rotary adsorption unit is a relatively inefficient system. A good deal of heat energy may not be fully utilized in these systems, and is lost.